Four out of 10 people are worried they cannot afford their next energy bill, according to research commissioned by Citizens Advice.

The charity, which helped clients with more than 96,000 fuel debt problems in 2011, also found that one in three people do not know that energy companies are offering support to insulate homes. It released the findings at the start of its Big Energy Week, which aims to help people save money on their bills.

Citzens Advice's chief executive, Gillian Guy, said: "Day in day out our bureaux help people who can't afford their fuel bills.

"We are worried that some people are struggling unnecessarily because they are not on the best deal, live in homes that haemorrhage heat, or are not getting all of the financial help available to them."

The study found that 43% of people are worried they cannot afford their next fuel bill, while one in two say energy bills will put a strain on their finances this year.

The charity said households who had never switched energy providers could make annual savings of up to £200 if they look for a different supplier, while switching from cheque to direct debit payments could save customers £100 a year.

The charity said that in November 2011 eight times as many people visited its website for advice on cutting their fuel bills compared to the previous November.

Energy secretary Chris Huhne, who is visiting Westfield shopping centre in west London to promote Big Energy Week, said: "We know that a lot of households are struggling to cope with rising energy costs.

"Many people could cut their gas and electricity bills by moving to a better deal with their existing supplier, switching to another supplier altogether, or by taking up home insulation offers.

"But we need to make sure consumers are aware of this and make it easier for them to take action to save money."